1. Field of the Invention
The present invention relates to an information device having a display unit such as a liquid crystal display (LCD), etc., and particularly to an information device in which the display unit has a plurality of display areas and power consumption can be controlled by controlling the plurality of display areas.
2. Description of the Related Art
Generally, in a portable information device, the device having an LCD (liquid crystal display) is frequently used. Normally, in an information displaying method on the display unit, one system is provided with one LCD, and information is displayed on a screen of LCD when power is turned on. According to a conventional dot-matrix type LCD, one LCD unit has a pair of drivers for driving an electrode for a display in each of X- and Y-axis directions. At a power-on time, electric power is supplied to the driver for each of the axial directions, and the entire LCD screen is driven.
It is required that the handy type information device be used for a long period time by a battery driving. For this reason, displaying information by use of the display device is preferably restricted to the necessary minimum in order to reduce power consumption.
However, there is a case in which certain information must be always represented, depending on a function formed in the handy type information device. In this case, the entire display screen must be always driven to display information on the LCD display screen. For example, it is assumed that there is provided a function for notifying a residual amount of the battery in the information device. In this case, information for showing the residual amount of the battery must be always represented. Due to this, the LCD screen is always driven to display such information on the LCD display screen.
In this case, there can be considered the use of an LED (light-emitting diode). In general, however, electric power, which is necessary for driving the LED, is much larger than electric power, which is necessary for driving the LCD.
As mentioned above, in the conventional information device, the entire LCD display must be always driven to always display certain information on the screen. As a result, a large amount of power is consumed, and time for driving the information device using the battery is reduced.